Mael Sechnaill mac Maele Ruanaid

Mael Sechnaill mac Maele Ruanaid (825-27 November 862), also known as Malachy MacMulrooney, was King of Mide from 845 to 862 (succeeding Fland mac Maele Ruanaid and preceding Lorcan mac Cathail) and High King of Ireland from 846 to 862 (succeeding Niall Caille and preceding Aed Findliath).

Biography
Mael Sechnaill mac Maele Ruanaid was born in 825 to the Colman sept of the O'Neill clan, and he killed his brother Fland mac Maele Ruanaid in 845 and usurped the kingdom of Mide from him; that same year, he heavily defeated the Vikings at Mag Itha and drowned their king Turgeis. In 846, he became High King of Ireland after Niall Caille drowned in the Callan River, and he frequently battled the Norse invaders and forced Ulster to recognize his high kingship. He died in 862.